The invention relates to friction clutches, for example, to friction clutches for use in motor vehicles. More particularly, the invention relates to improvements in friction clutches of the type wherein the means for connecting the clutch spring and its seat or seats to the clutch cover constitute or include integral parts of the cover.
Friction clutches of the above outlined character are known and enjoy widespread use in the automotive and other industries. Reference may be had, for example, to commonly owned U.S. Pat. No. 4,660,700 to Maucher et al. However, it has been found that presently known friction clutches wherein the spring is held at the inner side of the cover by integral parts of the cover (either alone or in combination with rivets or analogous fasteners) are not entirely satisfactory if the diameter of the clutch spring (such as a diaphragm spring) is rather large while the maximum diameter of the clutch is relatively small. The length of integral portions of the cover (these portions can be said to constitute lugs or beams) is then limited by the space which is available between the seat or seats for the clutch spring and the radially outermost portion of the cover. Therefore, the ratio of bias (force) to displacement of these relatively short beams is rather unsatisfactory. The characteristic curves of such beams are steep which results in pronounced hysteresis between the clutch engaging and disengaging forces of the clutch spring. This is also attributable to the fact that, in such types of friction clutches, that seat for the clutch spring which is remote from the inner side of the cover must be afforded a certain freedom of movement in a direction toward the cover in order to compensate for wear upon the parts in the region where the clutch spring is tilted during engagement or disengagement of the clutch.